PLASMA SOURCE MASS SPECTROMETRY  (ICP-MS) APPLICATION TO MULTI-ELEMENT ANALYSIS IN SEDIEMNT AND WATER SAMPLES

 

 

Oliveira, A.H.1,2 ; Severo, M.I.G2; Veado, M. A.R.V1; Mangabeira, P.A. O2; Galle, P2

Severo, G.G1 and Souza, R.B2

 

1-. Department of Nuclear Engineering - Universidade Federal de Minas Gerais, Av. do Contorno 842, CEP 30110-060 - Belo Horizonte, MG, Brazil ; e-mail: heeren@nuclear.ufmg.br

 

2 -Departement of Sciences Biological - University Santa Cruz, Km 18 Rodovia Ilhéus - Itabuna CEP 45650000, Ilhéus Bahia Brazil.; e-mail: severo@jacaranda.uescba.com.br

 

 

ABSTRACT

 

Inductively coupled plasma - mass spectrometry (ICP-MS) were used to determine of toxic heavy metals and other polluants in the aquatic environment of the the Cachoeira Rivers area. Water and sediment samples of the Cachoeira River in the state of Bahia, Brazil Elemental concentrations of Cu and Cr were measured in water and sediment samples collected in different sites of the Cachoeira River. The pollution in Copper is linked to the treatment of illnesses (Crinipellis perniciosa and Phytophthora sp) of the cocoa trees (Theobroma cocoa) and the pollution in Chromium  to the clandestine tannery industries. Five countrysides of taking, to one year of interval, have been done in three  diferents site of the Cachoeira River.

 

 

INTRODUCTION

 

Several metals occur in rivers and lakes from different domestic and industrial human activities, dead and decomposing animals and vegetatation, fallout of atmospheric particules and from rocks and soils exposed to surface waters (Babich and Stoztzky, 1983). Heavy metals are not biodegradable and enter the food chain througth a number of pathways causing progressive toxic actions due to the accumulation in different organs during a life span and long-term exposure to contaminated environments ( Forstener and Whittmann, 1979).

ICP-MS ( inductively coupled plasma mass spectrometry) has rapidly become established as a preferred method for the analysis of trace elements, in sediment and water samples, offering rapid analysis capabilities, an ability to measure most elements, relatively straightforward sample preparation, very low detection limits, a large dynamic range, and largely interference-free spectra. However, it is increasingly apparent that fully quantitative measurement by ICP-MS can be compromised  by variation in instrument sensitivity during the course of an  analytical run and with the introduction of different sample matrixes. Accurate and precise data may only be obtained if these effects can be minimised or, monitored and corrected for. Inductively coupled plasma mass spectrometry was used for the determination  the concentrations of several heavy metals  in water and sediments samples  in the Cachoeira River , Bahia – Brazil. The Cachoeira River is formed by the Colônia and Salgado rivers, measuring around  100 Km. These rivers flow into the main portion of the cocoa plantation  were large amounts of fungicides are applied as weed control of the mushrooms  (Crinipellis perniciosa and Phytophthora sp) in the cocoa.

 

 

METHODS

 

            Water and sediment samples were collected alond the Cachoeira River, from the region close to the Itapé P1 to P4  in one it  distance of  100 Km. Sampling areas are indicated in Fig. 1.

 

 

 

 

 

 

 


Fig.1– Area of study and sample sites in the Cachoeira River

 

Water samples were collected near the rivers bank at a depth of 15 cm, put into 125 ml bottles (Nalgene) stored at 4ºC. Temperature, pH and eletrical conductivity were mesured on sit.  The average values were: temperature 28°C, pH: 7.2, electrical conductivity: 30µS/cm (P1, P2 and P3)  The samples were acidified on site with 5 drops of ultrapure nitric acid (pH~2). This acidification is believed to reduce any sorption on the bottle walls (Mart, 1979). No filtration process was used in this study because it was tested and verified that filtration can be an important source of contamination (Veado et al., 1997,Veado, 1997). Before the analysis, all samples were centrifuged at 4 300 r·min-1 for 10 min to remove all suspended materials (Bailey et al., 1981; Laxen and Harrison, 1981). Sediment samples were collected in a 20 ml polyethylene tube. and also stored at a temperature of 4°C. They were dried for a day at a temperature of 80°C prior to analysis. One sediment sample was collected for each water sample at each sampling site.

The ICP-MS used in this study was a PlasmaQuad, PQ2+, with a Meinhard ultrasonic nebuliser, Laboratoire Pierre Süe –Comissariat à l’Energie Atomique, Saclay, France. A representative sediment sample from each sampling site(250 mg) was digested with a solution of HNO3 , HCl and HF under pressure at 110o C for 12 h, followed by another sequence of acid digestion, as demonstrated by Veado (1997b). To determine major elements (concentration higher than 50 g/l) the centrifuged river water was diluted twenty times using ultrapure water (Millipore). No dilution was made for trace element analysis. The internal standards for water and sediment samples were 10 mg/l solution of In, Re, and Be.

 

RESULTS AND DISCUSSION

 

The analytical methods were used to monitor elemental losses and contamination during analysis with international reference materials. The reference materials used were Riverine Water, SLRS-3 (National Research Council of Canada) and Soils-7 (International Atomic Energy, Vienna, Austria.). The results obtained using ICP-MS method for metal elements in this study were in agreement with certified values as shown in Tables 1 and 2. Analytical results obtained for the cachoeira  River are shown in figs. 2 to 8 Sampling sites P2 to P4  were located in the cocoa plantations. P1 was a estrategic point at a large  clandestine tannery activity, which discharges its directly into the river banks. The impact of this discharge is clearly shown in the high concentrations of Cr in the water and sediment samples of this site. An increase in the concentration of the elements analysed was observed in water and sediment samples from P4 . This occured despite the fact that P4  sampling were located upstream of the P1 (pollution in Chromium) and inside of the cocoa plantations ( pollution in Cooper).

 

                             TABLE 1

Results obtained (mg/l)  by INAA and ICP-MS                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             for Riverine Water Reference – SLRS 3

 

Element        Concentration Mesured   Certified Values

 

                       INAA          ICP-MS

 

Cr              0.38 ± 0.04     0.38 ± 0.04          0.30 ± 0.04

Cu                       -            1.5 ± 0.1            1.35 ± 0.07

Fe               110 ± 10        103 ± 20              100 ± 2

La               0.26 ± 0.03    0.26 ± 0.02            -

As               0.67 ± 0.07    0.67 ± 0.06         0.72 ± 0.05

 

 

 

                       TABLE 2

Results obtained ((mg/g) by INAA and ICP-MS

                       Reference – SOIL 7

 

Element  Concentration Measured   Certified values

 

                  INAA            ICP-MS    

 

Cr             63 ± 6            63  ± 2              60 ± 1

Cu                 -               13  ± 2              11 (9-13)

Fe             25700           25000               25700            

La             28 ± 3          28± 1                28 (27-29)

As             13.3± 1.3     14.8± 1.2        13.4(12-14 )

 

 

 


 

 


Fig. 2 – Concentration of Cu and Cr in the                 Fig. 3- Concentration of Cu and Cr in the                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  water – site P1                                                                    sediment – site P1

 


 Fig. 4 – Concentration of Cu and Cr in the                 Fig. 5- Concentration of Cu and Cr in the                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  water – site P3                                                                    sediment – site P3


 Fig. 6 – Concentration of Cu and Cr in the                        Fig. 7- Concentration of Cu and Cr in the                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 water – site P4                                                               sediment – site P4

                                                             

CONCLUSION

 

            The samples analysed were collected from three  areas within Cachoeiras  Rivers. The results (figs.2 to 7) indicate that Cu  and Cr concentrations   increase towards of the period  1995 to 1997  from three differents areas. Chromium is present in the highest concentrations levels  within P1 and

the higher copper  concentrations were found within P4 . These high concentration may be attributed  to  the largest   clandestine tannery industries ( Cr) and the pollution in Copper is linked to the treatment of illnesses (Crinipellis perniciosa and Phytophthora sp) of the cocoa (Theobroma cocoa).

            To minimize environmental hazards, the levels of potentially toxic elements need to be continuously monitored. ICP-MS proved to be a reliable, precise, accurate and efficient method with high sensitivity for the determination of ultra micro quantities of a large number of elements.

 

ACKNOWLEDGEMENT

 

This study was financed  by UESC ( Universidade Estadual de Santa Cruz ) and  CNPq ( Conselho Nacional de Desenvolvimento Científico e Tecnólogico).The authours are grateful for their assistence.

 

REFERENCES

 

-         H. Babich and G. Stotzky (1983), Ecol. Bull., 35: 315-323.

-         U. Forstner and G.T.W. Whittmann(1979), Springer, Berlin.

-         M. A.R.V. Veaddo, G. Pinte and  A.H. Oliveira (1997), Radioanal. Nucl. Chem. 217: 101-106

-         M. A..R.V. Veado (1997), Ph.D. Thesis, Orsay, France. 154pp.

-         R. A. Bailey, H.M. Clarke and J.P Ferris (1981), Chemistry the Environment